Sulfide solid electrolyte material, lithium solid-state battery, and method for producing sulfide solid electrolyte material

ABSTRACT

A sulfide solid electrolyte material contains glass ceramics that contains Li, A, X, and S, and has peaks at 2θ=20.2° and 23.6° in X-ray diffraction measurement with CuKα line. A is at least one kind of P, Si, Ge, Al, and B, and X is a halogen. A method for producing a sulfide solid electrolyte material includes amorphizing a raw material composition containing Li 2 S, a sulfide of A, and LiX to synthesize sulfide glass, and heating the sulfide glass at a heat treatment temperature equal to or more than a crystallization temperature thereof to synthesize glass ceramics having peaks at 2θ=20.2° and 23.6° in X-ray diffraction measurement with CuKα line, in which a ratio of the LiX contained in the raw material composition and the heat treatment temperature are controlled to obtain the glass ceramics.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sulfide solid electrolyte materialthat has high Li ion conductivity.

2. Description of Related Art

In recent years, as information-related devices and communicationdevices such as personal computers, video cameras, and portabletelephones are rapidly spreading, a development of batteries used aspower supply thereof is regarded as important. Further, also in anautomobile industry and so on, batteries for electric automobiles orhybrid automobiles, which have high output and high capacity, are underdevelopment. At the present time, among various kinds of batteries,lithium batteries are under attention from the viewpoint of high energydensity.

Lithium batteries that are commercially available at the present timeuse an electrolytic solution containing inflammable organic solvent, andaccordingly, a safety device that can prevent the temperature fromincreasing at the time of short-circuiting has to be provided and animprovement in structure and material for preventing theshort-circuiting is necessary. On the other hand, all-solid-statelithium batteries in which a solid electrolyte layer is used in place ofthe electrolytic solution do not contain inflammable organic solventtherein, and accordingly a safety device can be simplified. Theall-solid-state lithium batteries are thus considered to be superior inproduction costs and productivity. Further, as solid electrolytematerials usable for the solid electrolyte layer like this, sulfidesolid electrolyte materials have been known.

The sulfide solid electrolyte materials have high Li ion conductivityand are advantageous in realizing higher output of the battery, andaccordingly, various studies have been conducted thereon. For example,in Tomei et al., “Preparation of Amorphous Materials in the systemLiI—Li₂S—P₂S₅ by Mechanical Milling and Their Lithium Ion ConductingProperties”, Proceedings of The Symposium On Solid State Ionics, Vol.23, p. 26-27 (2003) (non-Patent Document 1), LiI—Li₂S—P₂S₅ systemamorphous materials obtained by mechanical milling are disclosed.Further, in F. Stader et al., “Crystalline halide substitutedLi-argyrodites as solid electrolyte for lithium ion batteries”, 216^(th)ECS (The Electrochemical Society) Meeting with EuroCVD 17 and SOFCXI-11^(th) International Symposium On Solid Oxide Fuel Cells, 2009,http://www.electrochem.org/meetings/scheduler/abstracts/216/0590.pdf(non-Patent Document 2), crystalline materials represented by Li₆PS₅X(X=Cl, Br, I) are disclosed.

SUMMARY OF THE INVENTION

Sulfide solid electrolyte materials having high Li ion conductivity arein demand. The present invention provides sulfide solid electrolytematerials having high Li ion conductivity.

After earnest studies were conducted, the present inventors found that,when synthesizing glass ceramics by heat-treating LiX-doped sulfideglass, in a limited range of each of addition amount of LiX and heattreatment temperature, glass ceramics having extremely high Li ionconductivity can be obtained. Further, the present inventors also foundthat the high Li ion conductivity is due to a novel crystalline phasethat has not been known. The present invention is achieved based onthese findings.

Namely, a first aspect of the present invention relates to a sulfidesolid electrolyte material. The sulfide solid electrolyte materialcontains a glass ceramics having Li, A, X, and S. A is at least oneelement of P, Si, Ge, Al and B, X is a halogen. The sulfide solidelectrolyte material has peaks at 2θ=20.2° and 23.6° in X-raydiffraction measurement with CuKα line.

According to the first aspect of the present invention, owing tospecified peaks in X-ray diffraction measurement, the sulfide solidelectrolyte material can have high Li ion conductivity.

In the sulfide solid electrolyte material, the glass ceramics mayinclude an ion conductor containing Li, A, and S, and LiX.

In the sulfide solid electrolyte material, a ratio of the LiX may be 14%by mole or more and less than 30% by mole.

In the sulfide solid electrolyte material, the ratio of the LiX may bemore than 14% by mole and less than 30% by mole.

In the sulfide solid electrolyte material, the ratio of the LiX may be25% by mole or less.

In the sulfide solid electrolyte material, the ion conductor may have anortho composition. This is because the sulfide solid electrolytematerial may have high chemical stability.

The sulfide solid electrolyte material may include 50% by mole or moreof a crystalline phase corresponding to the 2θ=20.2° and 23.6° relativeto a total crystalline phase of the sulfide solid electrolyte material.

A second aspect of the present invention relates to a lithiumsolid-state battery. The lithium solid-state battery includes a positiveelectrode active material layer containing a positive electrode activematerial, a negative electrode active material layer containing anegative electrode active material, and a solid electrolyte layer formedbetween the positive electrode active material layer and the negativeelectrode active material layer. At least one of the positive electrodeactive material layer, the negative electrode active material layer, andthe solid electrolyte layer includes the sulfide solid electrolytematerial described above.

According to the second aspect of the present invention, by use of thesulfide solid electrolyte material, a lithium solid-state battery havinghigh Li ion conductivity can be obtained. As the result thereof, outputpower of the lithium solid-state battery can be made higher.

A third aspect of the present invention relates to a lithium solid-statebattery. The lithium solid-state battery includes a positive electrodeactive material layer containing a positive electrode active material, anegative electrode active material layer containing a negative electrodeactive material, and a solid electrolyte layer formed between thepositive electrode active material layer and the negative electrodeactive material layer. At least one of the positive electrode activematerial layer, the negative electrode active material layer and thesolid electrolyte layer includes the sulfide solid electrolyte materialdescribed above. The LiX being LiI. The positive electrode activematerial has a potential of 2.8 V or more with respect to Li.

Further, a fourth aspect of the present invention relates to a methodfor producing a sulfide solid electrolyte material. The method forproducing a sulfide solid electrolyte material includes: amorphizing araw material composition containing Li₂S, a sulfide of A, and LiX tosynthesize sulfide glass; and heating the sulfide glass at a heattreatment temperature equal to or more than a crystallizationtemperature of the sulfide glass to synthesize glass ceramics havingpeaks at 2θ=20.2° and 23.6° in X-ray diffraction measurement with CuKαline. A is at least one element of P, Si, Ge, Al and B. X is a halogen.A ratio of the LiX contained in the raw material composition and theheat treatment temperature are controlled to obtain the glass ceramics.

According to the fourth aspect of the present invention, by controllingthe ratio of LiX contained in the raw material composition and the heattreatment temperature in the step of heating, sulfide solid electrolytematerials having high Li ion conductivity can be obtained.

In the method for producing a sulfide solid electrolyte material, theratio of the LiX contained in the raw material composition may be in afirst range of 14% by mole or more and less than 30% by mole or in asecond range in a vicinity of the first range and allows to synthesizethe glass ceramics, and an upper limit of the heat treatment temperatureis a temperature that allows to synthesize the glass ceramics in avicinity of 200° C.

In the method for producing a sulfide solid electrolyte material, theratio of the LiX contained in the raw material composition may be 14% bymole or more and less than 30% by mole, and the heat treatmenttemperature may be less than 200° C.

In the method for producing a sulfide solid electrolyte material, theheat treatment temperature may be 170° C. or more. In the method forproducing sulfide a solid electrolyte material, the heat treatmenttemperature may be 190° C. or less.

The present invention achieves the effect of obtaining sulfide solidelectrolyte materials having high Li ion conductivity.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments of the invention will be described below withreference to the accompanying drawings, in which like numerals denotelike elements, and wherein:

FIG. 1 is a schematic sectional view showing an example of a lithiumsolid-state battery of the present invention;

FIG. 2 is a flow chart showing an example of a method for producing asulfide solid electrolyte material of the present invention;

FIG. 3 shows results of X-ray diffraction measurements of glass ceramicsobtained in Examples 1 to 5;

FIG. 4 shows results of X-ray diffraction measurements of glass ceramicsobtained in Comparative Examples 2 to 4;

FIG. 5 shows results of measurements of Li ion conductivity of samplesobtained in Examples 1 to 5 and Comparative Examples 1 to 9;

FIG. 6 shows results of X-ray diffraction measurements of glass ceramicsobtained in Examples 6 to 8 and Comparative Example 11; and

FIG. 7 shows results of measurements of Li ion conductivity on samplesobtained in Examples 6 to 8 and Comparative Examples 10 to 11.

DETAILED DESCRIPTION OF EMBODIMENTS

A sulfide solid electrolyte material, a lithium solid-state battery, anda method for producing the sulfide solid electrolyte material will bedescribed below in details.

A. Sulfide Solid Electrolyte Material

Firstly, a sulfide solid electrolyte material according to an embodimentof the invention will be described. The sulfide solid electrolytematerial of the embodiment of the invention is glass ceramics thatcontains Li, A (A is at least one kind of P, Si, Ge, Al and B), X (X isa halogen) and S, and has peaks at 2θ=20.2° and 23.6° in X-raydiffraction measurement with CuKα line.

According to the invention, owing to specified peaks in X-raydiffraction measurement, the sulfide solid electrolyte materials havinghigh Li ion conductivity can be obtained. These peaks are peaks of anovel crystalline phase that is unknown until now. Since the Li ionconductivity of the novel crystalline phase is high, the Li ionconductivity of the sulfide solid electrolyte material can be improved.

Further, since the sulfide solid electrolyte material according to theembodiment of the invention is glass ceramics, it has an advantage thatthe heat resistance thereof is higher than that of sulfide glass. Forexample, when LiI is doped in Li₂S—P₂S₅ system sulfide glass, the Li ionconductivity can be enhanced. However, when LiI is doped, in some cases,the crystallization temperature of the sulfide glass can be lowered. Inthe case where the sulfide glass of which crystallization temperature islow is used in, for example, a battery, when a temperature of thebattery reaches the crystallization temperature of the sulfide glass ormore, heat generation caused by crystallization of the sulfide glassoccurs. As the result thereof, the respective materials configuring thebattery may be altered (deteriorated) or a battery case and so on may bedamaged. On the other hand, according to the present invention, bypreparing glass ceramics crystallized in advance, the sulfide solidelectrolyte material in which adverse affect of heat generation due tocrystallization is inhibited can be obtained. Further, there areadvantages also in that a cooling mechanism and a safety mechanism forthe battery can be simplified.

Further, in Tomei et al., “Preparation of Amorphous Materials in thesystem LiI—Li₂S—P₂S₅ by Mechanical Milling and Their Lithium IonConducting Properties”, Proceedings of The Symposium On Solid StateIonics, Vol. 23, p. 26-27 (2003) (non-Patent Document 1), LiI—Li₂S—P₂S₅system amorphous materials obtained by mechanical milling are disclosed.However, in the non-Patent Document 1, the heat treatment of theLiI—Li₂S—P₂S₅ system sulfide glass is neither disclosed nor indicated.Further, even when the LiI—Li₂S—P₂S₅ system sulfide glass isheat-treated, in order to precipitate the novel crystalline phase, it isnecessary to adjust a ratio of LiI and a heat treatment temperature.However, there is no indication thereof in the non-Patent Document 1. Onthe other hand, in F. Stader et al., “Crystalline halide substitutedLi-argyrodites as solid electrolyte for lithium ion batteries”, 216^(th)ECS (The Electrochemical Society) Meeting with EuroCVD 17 and SOFCXI-11^(th) International Symposium On Solid Oxide Fuel Cells, 2009,http://www.electrochem.org/meetings/scheduler/abstracts/216/0590.pdf(non-Patent Document 2), crystalline materials represented by Li₆PS₅X(X=Cl, Br, I) are disclosed. However, it is also disclosed that when Iis added, the Li ion conductivity of the crystalline material isdeteriorated. Namely, it is indicated that the Li ion conductivitycannot be improved in crystal (glass ceramics) merely by addition ofhalogen.

The sulfide solid electrolyte material of the embodiment of theinvention may be glass ceramics. The glass ceramics of the inventionrefers to a material obtained by crystallizing sulfide glass. Whether itis glass ceramics can be confirmed by, for example, X-ray diffraction.Further, the sulfide glass refers to a material that is synthesized byamorphizing raw material compositions, including not only an exact“glass” in which the periodicity as crystal is not observed in X-raydiffraction measurement, but also materials in general that aresynthesized by amorphizing by mechanical milling that will be describedbelow. Accordingly, even when, in X-ray diffraction measurement and soon, peaks derived from, for example, raw materials (Li and so on) areobserved, as long as a material is synthesized by amorphizing, itcorresponds to sulfide glass.

The sulfide solid electrolyte material according to the embodiment ofthe invention has peaks at 2θ=20.2° and 23.6° in X-ray diffractionmeasurement with CuKα line. These peaks are peaks of a novel crystallinephase that is unknown until now and has high Li ion conductivity.Hereinafter, in some cases, the crystalline phase is referred to as acrystalline phase having high Li ion conductivity. Here, a peak at2θ=20.2° refers to not only a peak exactly at 2θ=20.2°, but also a peakin the range of 2θ=20.2° ±0.5°. Depending on a state of the crystal, aposition of the peak can be varied slightly, and accordingly, thedefinition as mentioned above is adopted. Similarly, a peak at 2θ=23.6°refers to not only a peak exactly at 2θ=23.6°, but also a peak in therange of 2θ=23.6° ±0.5°. The sulfide solid electrolyte materialaccording to the embodiment of the invention preferably mainly has thecrystalline phase having high Li ion conductivity. Specifically, a ratioof the crystalline phase having high Li ion conductivity is preferably50% by mole or more in an entire crystalline phase.

On the other hand, the sulfide solid electrolyte material according tothe embodiment of the invention has, in some cases, peaks at 2θ=21.0°and 28.0° in X-ray diffraction measurement with CuKα line. These peakswere found by our studies and are peaks of a novel crystalline phasethat is unknown until now, as described above, and that has the Li ionconductivity lower than the high Li ion conductivity crystalline phase.Hereinafter, in some cases, the crystalline phase is referred to as acrystalline phase having low Li ion conductivity. Here, a peak at2θ=21.0° refers to not only a peak exactly at 2θ=21.0°, but also a peakin the range of 2θ=21.0° ±0.5°. Depending on a state of the crystal, aposition of the peak can be varied slightly, and accordingly, thedefinition as mentioned above is adopted. Similarly, a peak at 2θ=28.0°refers to not only a peak exactly at 2θ=28.0°, but also a peak in therange of 2θ=28.0° ±0.5°. The sulfide solid electrolyte materialaccording to the embodiment of the invention preferably contains the lowLi ion conductivity crystalline phase at a lower ratio.

Further, it can be determined from results of X-ray diffractionmeasurement that the sulfide solid electrolyte material according to theembodiment of the invention has specified peaks. On the other hand, forexample, when a ratio of the crystalline phase having high Li ionconductivity is low and a ratio of the crystalline phase having low Liion conductivity is high, peaks at 2θ=20.2° and 23.6° appear smaller,and peaks at 2θ=21.0° and 28.0° appear larger. Now, a ratio of a peakintensity at 2θ=20.2° to a peak intensity at 2θ=21.0° is expressed asI_(20.2)/I_(21.0), and a ratio of a peak intensity at 2θ=23.6° to a peakintensity at 2θ=21.0° is expressed as I_(23.6)/I_(21.0). The sulfidesolid electrolyte material of the embodiment of the invention isdetermined to have peaks at 2θ=20.2° and 23.6° from each ofI_(20.2)/I_(21.0) and I_(23.6)/I_(21.0) of 0.1 or more (preferably 0.2or more). In the embodiment of the invention, I_(20.2)/I_(21.0) ispreferably 1 or more. This is because a sulfide solid electrolytematerial with a high ratio of the crystalline phase having high Li ionconductivity can be obtained.

The sulfide solid electrolyte material of the embodiment of theinvention includes Li, A (A is at least one kind of P, Si, Ge, Al andB), X (X is a halogen), and S. On the other hand, as described above,the sulfide solid electrolyte material of an embodiment of the inventionhas specified peaks in X-ray diffraction measurement. Here, the X-raydiffraction measurement is a method in which by analyzing results ofdiffraction of X-rays from a crystal lattice, an atomic arrangement in acrystal is specified. Accordingly, from the principle, a pattern ofpeaks in X-ray diffraction measurement depends on a crystal structure,but not largely depends on kinds of atoms configuring the crystalstructure. Accordingly, irrespective of kinds of A and X, when the samecrystal structure is formed, a similar pattern can be obtained. Namely,irrespective of kinds of A and X, when a crystalline phase having highLi ion conductivity is formed, a similar pattern can be obtained. Aposition of the pattern can be varied slightly. Also from thisviewpoint, peaks at 2θ=20.2° and 23.6° are preferably defined in a rangeof 2θ=20.2° ±0.5° and 23.6° ±0.5°, respectively.

Further, the sulfide solid electrolyte material of the embodiment of theinvention is preferably configured of an ion conductor that includes Li,A (A is at least one kind of P, Si, Ge, Al and B), and S, and LiX (X isa halogen). At least a part of LiX is usually present incorporated in astructure of the ion conductor as a LiX component.

The ion conductor of the embodiment of the invention includes Li, A (Ais at least one kind of P, Si, Ge, Al and B), and S. The ion conductoris not particularly limited as long as it includes Li, A, and S.However, among these, the ion conductor having an ortho composition ispreferred. This is because a sulfide solid electrolyte material havinghigh chemical stability can be obtained. Here, the ortho generallyrefers to an oxo acid with the highest degree of hydration among oxoacids obtained by hydrating the same oxide. In the embodiment of theinvention, a crystal composition of sulfide to which Li₂S is most addedis referred to as ortho composition. For example, in an Li₂S—P₂S₅system, Li₃PS₄ corresponds to the ortho composition, in an Li₂S—Al₂S₃system, Li₃AlS₃ corresponds to the ortho composition, in an Li₂S—B₂S₃system, Li₃BS₃ corresponds to the ortho composition, in an Li₂S—SiS₂system, Li₄SiS₄ corresponds to the ortho composition, and in anLi₂S—GeS₂ system, Li₄GeS₄ corresponds to the ortho composition.

Further, in the embodiment of the present invention, “having an orthocomposition” includes not only an exact ortho composition, but also acomposition in the vicinity thereof. Specifically, “having an orthocomposition” means that an anion structure of the ortho composition (PS₄³⁻ structure, SiS₄ ⁴⁻ structure, GeS₄ ⁴⁻ structure, AlS₃ ³⁻ structure,and BS₃ ³⁻ structure) is mainly contained. A ratio of the anionstructure of the ortho composition relative to a total anion structurein an ion conductor is preferably 60% by mole or more, more preferably70% by mole or more, still more preferably 80% by mole or more, andparticularly preferably 90% by mole or more. The ratio of the anionstructure of the ortho composition can be determined by use of Ramanspectrometry, NMR, XPS and so on.

Further, the sulfide solid electrolyte material of the embodiment of theinvention is preferably obtained in such a manner that a raw materialcomposition containing Li₂S, sulfide of A (A is at least one kind of P,Si, Ge, Al and B), and LiX (X is a halogen) is amorphized and furtherheat-treated.

The Li₂S contained in the raw material composition preferably containsless impurities. This is because a side reaction can be suppressed. As amethod for synthesizing Li₂S, a method described in, for example,Japanese Patent Application Publication No. 07-330312 (JP 07-330312 A)and so on can be cited. Further, Li₂S is preferably purified by use of amethod described in WO2005/040039. On the other hand, as the sulfide ofA contained in the raw material composition, P₂S₃, P₂S₅, SiS₂, GeS₂,Al₂S₃, B₂S₃ and so on can be cited.

Further, the sulfide solid electrolyte material preferably does notsubstantially contain Li₂S. This is because a sulfide solid electrolytematerial generating a smaller amount of hydrogen sulfide can beobtained. When Li₂S reacts with water, hydrogen sulfide is generated.For example, when a ratio of Li₂S contained in the raw materialcomposition is high, Li₂S tends to remain. Whether the sulfide solidelectrolyte material “does not substantially contain Li₂S” can beconfirmed by X-ray diffractometry. Specifically, when peaks of Li₂S(2θ=27.0°, 31.2°, 44.8° and 53.1°) are not contained, the sulfide solidelectrolyte material is determined not to substantially contain Li₂S.

Still further, the sulfide solid electrolyte material preferably doesnot substantially contain cross-linked sulfur. This is because a sulfidesolid electrolyte material generating a smaller amount of hydrogensulfide can be obtained. The “cross-linked sulfur” refers tocross-linked sulfur in a compound formed by a reaction between Li₂S andthe sulfide of A. For example, cross-linked sulfur having an S₃P—S—PS₃structure that is formed by a reaction between Li₂S and P₂S₅ correspondsto this. This cross-linked sulfur tends to react with water and tends togenerate hydrogen sulfide. Further, whether sulfide solid electrolytematerial “does not substantially contain cross-linked sulfur” can beconfirmed by Raman spectrum measurement. For example, in the case of theLi₂S—P₂S₅ system sulfide solid electrolyte material, a peak of theS₃P—S—PS₃ structure usually appears at 402 cm^(−I). Accordingly, it ispreferable that the peak is not detected. Further, a peak of a PS₄ ³⁻structure usually appears at 417 cm⁻¹. In the embodiment of the presentinvention, an intensity I₄₀₂ at 402 cm⁻¹ is preferably smaller than anintensity I₄₁₇ at 417 cm⁻¹. More specifically, relative to the intensityI₄₁₇, the intensity I₄₀₂ is preferably, for example, 70% or less, morepreferably 50% or less, and still more preferably 35% or less. Further,whether a sulfide solid electrolyte material other than the Li₂S—P₂S₅system sulfide solid electrolyte material does not substantially containthe cross-linked sulfur can be determined by specifying a unitcontaining the crosslinked sulfur and by measuring a peak of the unit.

Further, in the case of the Li₂S—P₂S₅ system sulfide solid electrolytematerial, a ratio of Li₂S and P₂S₅ for obtaining the ortho compositionis, by mole, Li₂S:P₂S₅=75:25. The same ratio is also applied to both thecase of the Li₂S—Al₂S₃ system sulfide solid electrolyte material and thecase of the Li₂S—B₂S₃ system sulfide solid electrolyte material. On theother hand, in the case of the Li₂S—SiS₂ system sulfide solidelectrolyte material, a ratio of Li₂S and SiS₂ for obtaining the orthocomposition is, by mole, Li₂S:SiS₂=66.7:33.3. The same ratio is alsoapplied to the case of the Li₂S—GeS₂ system sulfide solid electrolytematerial.

In the case where the raw material composition contains Li₂S and P₂S₅, aratio of Li₂S to a sum total of Li₂S and P₂S₅ is set preferably in therange of 70% by mole to 80% by mole, more preferably in the range of 72%by mole to 78% by mole, and still more preferably in the range of 74% bymole to 76% by mole. The ratio set in the same range is also applied toboth the case where the raw material composition contains Li₂S and Al₂S₃and the case where the raw material composition contains Li₂S and B₂S₃.On the other hand, in the case where the raw material compositioncontains Li₂S and SiS₂, a ratio of Li₂S to a sum total of Li₂S and SiS₂is set preferably in the range of 62.5% by mole to 70.9% by mole, morepreferably in the range of 63% by mole to 70% by mole, and still morepreferably in the range of 64% by mole to 68% by mole. The ratio set inthe same range is also applied to the case where the raw materialcomposition contains Li₂S and GeS₂.

Now, X in LiX is a halogen that is specifically F, Cl, Br and I. Amongthese, Cl, Br and I are preferable. This is because a sulfide solidelectrolyte material having high ion conductivity can be obtained.Further, a ratio of LiX in the sulfide solid electrolyte material of theembodiment of the invention is not particularly limited as long as itallows to synthesize desired glass ceramics. However, for example, theratio of LiX is preferably in the range of 14% by mole or more and 30%by mole or less, and more preferably in the range of 15% by mole or moreand 25% by mole or less.

The sulfide solid electrolyte material of the embodiment of theinvention is in the form of particles, for example. An average particlesize (D50) of the sulfide solid electrolyte material in the form ofparticles is preferably in the range of, for example, 0.1 μm to 50 μm.Further, the sulfide solid electrolyte material preferably has high Liion conductivity. The Li ion conductivity thereof at room temperature ispreferably, for example, 1×10⁻⁴ S/cm or more, and more preferably 1×10⁻³S/cm or more.

The sulfide solid electrolyte material of the embodiment of theinvention can be used in any applications that need the Li ionconductivity. Among these, the sulfide solid electrolyte material ispreferably used in batteries.

B. Lithium Solid-State Battery

Next, a lithium solid-state battery of an embodiment of the inventionwill be described. A lithium solid-state battery of an embodiment of theinvention includes a positive electrode active material layer containinga positive electrode active material, a negative electrode activematerial layer containing a negative electrode active material, and asolid electrolyte layer formed between the positive electrode activematerial layer and the negative electrode active material layer, and atleast one of the positive electrode active material layer, the negativeelectrode active material layer and the solid electrolyte layer containsthe sulfide solid electrolyte material.

According to the embodiment of the present invention, by use of thesulfide solid electrolyte material, the lithium solid-state batteryhaving high Li ion conductivity can be obtained. As the result thereof,output power of the lithium battery can be made higher.

FIG. 1 is a schematic sectional view showing an example of the lithiumsolid-state battery of the embodiment of the invention. A lithiumsolid-state battery 10 shown in FIG. 1 includes a positive electrodeactive material layer 1 containing a positive electrode active material,a negative electrode active material layer 2 containing a negativeelectrode active material, a solid electrolyte layer 3 formed betweenthe positive electrode active material layer 1 and the negativeelectrode active material layer 2, a positive electrode collector 4 thatcollects current of the positive electrode active material layer 1, anda negative electrode collector 5 that collects current of the negativeelectrode active material layer 2. In the embodiment of the invention,at least one of the positive electrode active material layer 1, thenegative electrode active material layer 2 and the solid electrolytelayer 3 includes the sulfide solid electrolyte material described in the“A. Sulfide Solid Electrolyte Material”. Respective constituents of thelithium solid-state battery of the embodiment of the invention will bedescribed below.

1. Positive Electrode Active Material Layer

Firstly, a positive electrode active material layer in an embodiment ofthe invention will be described. The positive electrode active materiallayer in the embodiment of the invention is a layer that contains atleast a positive electrode active material, and may further contain atleast one of a solid electrolyte material, a conductive material and abinder, as required.

In the embodiment of the invention, a solid electrolyte materialcontained in the positive electrode active material layer is preferablythe sulfide solid electrolyte material described in the “A. SulfideSolid Electrolyte Material”. A content of the sulfide solid electrolytematerial in the positive electrode active material layer is preferably,for example, in the range of 0.1% by volume to 80% by volume, morepreferably in the range of 1% by volume to 60% by volume, andparticularly in the range of 10% by volume to 50% by volume.

Examples of the positive electrode active materials include, but notparticularly limited to, rock salt layer like active materials such asLiCoO₂, LiMnO₂, LiNiO₂, LiVO₂ and LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂,spinel-type active materials such as LiMn₂O₄ and Li(Ni_(0.5)Mn_(1.5))O₄,and olivine-type active materials such as LiFePO₄, LiMnPO₄, LiNiPO₄ andLiCuPO₄. Further, also silicon-containing oxides such as Li₂FeSiO₄ andLi₂MnSiO₄ may be used as the positive electrode active material.

In particular, when the sulfide solid electrolyte material has an ionconductor having an ortho composition and is formed with LiI, thepositive electrode active material has preferably a potential of 2.8 V(vs. Li) or more and more preferably has a potential of 3.0 V (vs. Li)or more. This is because LiI can be effectively inhibited from oxidativedecomposition. Since LiI has been considered to be decomposed in thevicinity of 2.8 V, a sulfide solid electrolyte material having LiI hasnot been used in a positive electrode active material layer. Incontrast, the sulfide solid electrolyte material has an ion conductorhaving the ortho composition, and accordingly, it is considered that LiIis stabilized via an interaction with the ion conductor, therebyinhibiting LiI from oxidative decomposition.

The positive electrode active material is in the form of particles, forexample, and preferably in the form of a true sphere or an oval sphere.Further, when the positive electrode active material is in the form ofparticles, an average particle size thereof is preferably in the rangeof, for example, 0.1 μm to 50 μm. Still further, a content of thepositive electrode active material in the positive electrode activematerial layer is preferably in the range of, for example, 10% by volumeto 99% by volume, and more preferably in the range of 20% by volume to99% by volume.

The positive electrode active material layer in the embodiment of theinvention may further contain, other than the positive electrode activematerial and the solid electrolyte material, at least one of aconductive material and a binder. Examples of the conductive materialinclude acetylene black, Ketjen black, carbon fiber and so on. Examplesof the binder include fluorine-containing binders such as PTFE and PVDF.A thickness of the positive electrode active material layer ispreferably in the range of, for example, 0.1 μm to 1000 μm.

2. Negative Electrode Active Material Layer

Next, a negative electrode active material layer in the embodiment ofthe invention will be described. The negative electrode active materiallayer of the embodiment of the invention is a layer that contains atleast a negative electrode active material and may further contain atleast one of a solid electrolyte material, a conductive material and abinder, as required.

In the embodiment of the invention, a solid electrolyte materialcontained in the negative electrode active material layer is preferablythe sulfide solid electrolyte material described in the “A. SulfideSolid Electrolyte Material”. A content of the sulfide solid electrolytematerial in the negative electrode active material layer is preferably,for example, in the range of 0.1% by volume to 80% by volume, morepreferably, in the range of 1% by volume to 60% by volume, andparticularly in the range of 10% by volume to 50% by volume.

Examples of the negative electrode active material include metal activematerials and carbon active materials. Examples of the metal activematerial include In, Al, Si and Sn. On the other hand, examples of thecarbon active materials include mesocarbon microbeads (MCMB), highlyordered pyrolytic graphite (HOPG), hard carbon, soft carbon and so on. Acontent of the negative electrode active material in the negativeelectrode active material layer is preferably in the range of 10% byvolume to 99% by volume, for example, and more preferably in the rangeof 20% by volume to 99% by volume. Both the conductive material and thebinder are the same as those used in the positive electrode activematerial layer. A thickness of the negative electrode active materiallayer is preferably in the range of 0.1 μm to 1000 μm, for example.

3. Solid Electrolyte Layer

Next, the solid electrolyte layer of the embodiment of the inventionwill be described. The solid electrolyte layer of the embodiment of theinvention is a layer that is formed between the positive electrodeactive material layer and the negative electrode active material layerand configured of a solid electrolyte material. The solid electrolytematerial contained in the solid electrolyte layer is not particularlylimited as long as it has the Li ion conductivity.

In the invention, the solid electrolyte material contained in the solidelectrolyte layer is preferably the sulfide solid electrolyte materialdescribed in the “A. Sulfide Solid Electrolyte Material.” A content ofthe sulfide solid electrolyte material in the solid electrolyte layer isnot particularly limited as long as desired insulating properties areobtained. The content of the sulfide solid electrolyte material ispreferably in the range of 10% by volume to 100% by volume, for example,and more particularly in the range of 50% by volume to 100% by volume.In particular, in the present invention, the solid electrolyte layer ispreferably configured only of the sulfide solid electrolyte material.

Further, the solid electrolyte layer may contain a binder. This isbecause when the binder is contained, the solid electrolyte layer havingflexibility can be obtained. Examples of the binder includefluorine-containing binders such as PTFE and PVDF. A thickness of thesolid electrolyte layer is preferably in the range of 0.1 μm to 1000 μm,and more preferably in the range of 0.1 μm to 300 μm.

4. Other Configuration

The lithium solid-state battery of the embodiment of the inventionincludes at least the positive electrode active material layer, thenegative electrode active material layer, and the solid electrolytelayer. Further, usually, the lithium solid-state battery includes apositive electrode collector that collects current of the positiveelectrode active material layer, and a negative electrode collector thatcollects current of the negative electrode active material layer.Examples of the material of the positive electrode collector includeSUS, aluminum, nickel, iron, titanium, carbon and so on. Among these,SUS is preferable. On the other hand, examples of the material of thenegative electrode collector include SUS, copper, nickel, carbon and soon. Among these, SUS is preferable. Further, a thickness, a shape and soon of the positive electrode collector and negative electrode collectorare preferably selected appropriately in accordance with usages and soon of the lithium solid-state battery. Still furthermore, as a batterycase used in the invention, a battery case for general lithiumsolid-state batteries can be used. An example of the battery caseincludes an SUS battery case.

5. Lithium Solid-State Battery

The lithium solid-state battery of the embodiment of the invention maybe a primary battery or a secondary battery. However, the secondarybattery is preferable. This is because the secondary battery can berepeatedly charged and discharged and is useful as a battery forautomobiles. Examples of a shape of the lithium solid-state battery ofthe embodiment of the invention include a coin shape, a laminate shape,a cylinder shape, and a rectangular shape.

Further, the method for producing a lithium solid-state battery of theembodiment of the invention is not particularly limited as long as theabove-described lithium solid-state battery can be produced. Namely, ageneral method for producing a lithium solid-state battery can also beused. Examples of the method for producing a lithium solid-state batteryinclude a method in which a material that configures a positiveelectrode active material layer, a material that configures a solidelectrolyte layer, and a material that configures a negative electrodeactive material layer are sequentially pressed to prepare anelectricity-generating element, the electricity-generating element ishoused inside of a battery case, and the battery case is caulked, and soon.

C. Method for Producing Sulfide Solid Electrolyte Material

Next, a method for producing the sulfide solid electrolyte material ofthe embodiment of the invention will be described. The method forproducing the sulfide solid electrolyte material of the embodiment ofthe invention includes the steps of: amorphizing a raw materialcomposition containing Li₂S, a sulfide of A (A is at least one kind ofP, Si, Ge, Al, and B), and LiX (x is a halogen) to synthesize sulfideglass; and heating the sulfide glass at a temperature equal to or morethan a crystallization temperature thereof to synthesize glass ceramicshaving peaks at 2θ=20.2° and 23.6° in X-ray diffraction measurement withCuKα line, in which a ratio of the LiX contained in the raw materialcomposition and a heat treatment temperature in the step of heating thesulfide glass are adjusted to obtain the glass ceramics.

FIG. 2 is a flowchart showing an example of the method for producing asulfide solid electrolyte material of the embodiment of the invention.In FIG. 2, firstly, a raw material composition containing LiI, Li₂S andP₂S₅ is prepared. Then, the raw material composition is mechanicallymilled to synthesize sulfide glass containing an ion conductor (forexample, Li₃PS₄) containing Li, P, and S, and LiI. Next, the sulfideglass is heated at a temperature equal to or more than thecrystallization temperature thereof to obtain glass ceramics (sulfidesolid electrolyte material) having peaks at 2θ=20.2° and 23.6° in X-raydiffraction measurement with CuKα line.

According to the invention, when the ratio of the LiX contained in theraw material composition and the heat treatment temperature in the stepof heating the sulfide glass are adjusted, a sulfide solid electrolytematerial having high Li ion conductivity can be obtained. The method forproducing the sulfide solid electrolyte material of the embodiment ofthe invention will be described below for each step.

1. Amorphizing Step

The amorphizing step in the embodiment of the invention is a step ofamorphizing a raw material composition containing Li₂S, a sulfide of A(A is at least one kind of P, Si, Ge, Al and B), and LiX (x is ahalogen) to synthesize sulfide glass

Now, Li₂S, a sulfide of A (A is at least one kind of P, Si, Ge, Al, andB), and LiX (x is a halogen) in the raw material composition are thesame as those described in the “A. Sulfide Solid Electrolyte Material,”and accordingly, description thereof will be omitted. A ratio of LiX inthe raw material composition is not particularly limited as long as itallows to synthesize desired glass ceramics and varies slightlydepending on a synthesis condition. The ratio of LiX in the raw materialcomposition is preferably in the range of 14% by mole to 30% by mole orin the range of the vicinity thereof, which allows to synthesize theglass ceramics. Under the conditions of examples described below, whenthe ratio of LiX is more than 14% by mole and less than 30% by mole,desired glass ceramics could be obtained.

Examples of a method for amorphizing the raw material compositioninclude a mechanical milling method and a melt quenching method. Amongthese, the mechanical milling method is preferred. This is because themechanical milling method allows to process at room temperature tosimplify the producing process. Further, while the melt quenching methodis limited by a reaction atmosphere and a reaction vessel, themechanical milling method is advantageous in that sulfide glass having atargeted composition can be conveniently synthesized. The mechanicalmilling method may be a dry mechanical milling method or a wetmechanical milling method. However, the wet mechanical milling method ispreferred. This is because the raw material composition can be inhibitedfrom adhering to a wall surface of the vessel to enable to obtainsulfide glass having higher amorphous properties.

The method of mechanical milling is not particularly limited as long asit can mix the raw material composition while imparting mechanicalenergy. Examples of the method include a ball mill, a vibration mill, aturbo-mill, a mechanofusion mill, and a disc mill. Among these, the ballmill is preferable, and, a satellite ball mill is particularlypreferable. This is because desired sulfide glass can be efficientlyobtained.

Various kinds of conditions of the mechanical milling are set so as toobtain desired sulfide glass. For example, when a satellite ball mill isused, a raw material composition and pulverizing balls are charged in avessel and treated at a predetermined rotation speed for a predeterminedtime. In general, the higher the rotation speed is, the higher the speedof generation of the sulfide glass is, and the longer a processing timeis, the higher the conversion rate from the raw material composition tothe sulfide glass is. The rotation speed of a base when a satellite ballmill is used is, for example, in the range of 200 rpm to 500 rpm, andpreferably in the range of 250 rpm to 400 rpm. Further, a processingtime when the satellite ball mill is used is set, for example, in therange of one hour to 100 hours, and preferably in the range of one hourto 50 hours. Examples of materials for the vessel and the pulverizingballs for the ball mill include ZrO₂ and Al₂O₃. Further, a diameter ofthe pulverizing balls is, for example, in the range of 1 mm to 20 mm.

A liquid used for the wet mechanical milling preferably has a propertythat does not generate hydrogen sulfide during reaction with the rawmaterial composition is preferred. Hydrogen sulfide is generated whenprotons dissociated from molecules of the liquid react with the rawmaterial composition or sulfide glass. Accordingly, the liquidpreferably has non-proton properties to an extent that does not generatehydrogen sulfide. Further, the non-protonic liquid can be usuallyroughly divided into polar non-protonic liquid and nonpolar nonprotonicliquid.

Examples of the polar nonprotonic liquid include, but not particularlylimited to, ketones such as acetone, nitriles such as acetonitrile,amides such as N,N-dimethyl formamide (DMF), and sulfoxides such asdimethylsulfoxide (DMSO).

Examples of the nonpolar nonprotonic liquid include an alkane that is inthe form of liquid at room temperature (25° C.). The alkane may be achain alkane or a cyclic alkane. The chain alkane preferably has carbonatoms of 5 or more. On the other hand, the upper limit of the number ofcarbon atoms of the chain alkane is not particularly limited as long asit is in the form of liquid at room temperature. Specific examples ofthe chain alkane include pentane, hexane, heptane, octane, nonane,decane, undecane, dodecane, and paraffin. The chain alkane may have abranched chain. On the other hand, specific examples of the cyclicalkane include cyclopentane, cyclohexane, cycloheptane, cyclooctane, andcycloparaffin.

Further, other examples of the nonpolar nonprotonic liquid includearomatic hydrocarbons such as benzene, toluene, and xylene, chain etherssuch as diethyl ether and dimethyl ether, cyclic ethers such astetrahydrofuran, halogenated alkyls such as chloroform, methyl chloride,and methylene chloride, esters such as ethyl acetate, andfluorocompounds such as benzene fluoride, heptane fluoride,2,3-dihydroperfluoropentane, and 1,1,2,2,3,3,4-heptafluorocyclopentane.An addition amount of the liquid is not particularly limited as long asit is an amount to an extent that allows to obtain a desired sulfidesolid electrolyte material.

2. Heating Step

Next, the heating step in the embodiment of the invention will bedescribed. The heating step in the embodiment of the invention is a stepof heating the sulfide glass to a temperature equal to or more than thecrystallization temperature thereof to synthesize glass ceramics havingpeaks at 2θ=20.2° and 23.6° in X-ray diffraction measurement with CuKαline.

The heat treatment temperature is usually a temperature equal to or morethan the crystallization temperature of sulfide glass. Thecrystallization temperature of the sulfide glass can be determined bydifferential thermal analysis (DTA). The heat treatment temperature isnot particularly limited as long as it is a temperature equal to orhigher than the crystallization temperature. However, it is preferably,for example, 160° C. or higher. On the other hand, the upper limit ofthe heat treatment temperature is not particularly limited as long as itis a temperature that allows to synthesize desired glass ceramics andvaries slightly depending on a composition of the sulfide glass. Theupper limit of the heat treatment temperature is usually a temperaturethat is in the vicinity of 200° C. and allows to synthesize the glassceramics. Under the conditions of examples described below, when theheat treatment temperature is less than 200° C., desired glass ceramicscould be obtained.

The heat treatment time is not particularly limited as long as the heattreatment time allows to obtain desired glass ceramics, and, preferablyin the range of, for example, one minute to 24 hours. Further, the heattreatment is preferably conducted in an inert gas atmosphere (forexample, Ar gas atmosphere). This is because the glass ceramics can beinhibited from deteriorating (for example, oxidation). A method of theheat treatment is not particularly limited. For example, a method thatuses a firing furnace can be used.

The above embodiments are only for illustrative purpose, and anythingthat has substantially the same constitution and produces the sameeffects as a technical idea that is described in the claims of thepresent invention is included in the technical scope of the presentinvention.

EXAMPLES

The present invention will be more specifically described below withreference to examples. Unless clearly stated otherwise, the respectiveoperations of weighting, synthesis, drying and so on were conductedunder Ar atmosphere.

Example 1

As starting raw materials, lithium sulfide (Li₂S, manufactured by NipponChemical Industrial Co., Ltd.), phosphorus pentasulfide (P₂S₅,manufactured by Aldrich Corporation) and lithium iodide (LiI,manufactured by Aldrich Corporation) were used. Then, Li₂S and P₂S₅ weremeasured to be 75Li₂S·25P₂S₅ by mole ratio (Li₃PS₄, ortho composition).Next, LiI was measured so that a ratio of LiI may be 14% by mole. Themeasured starting raw materials were mixed in an agate mortar for 5minutes, 2 g of the mixture was charged in a vessel (45 cc, ZrO₂) of asatellite ball mill, dewatered heptane (water content: 30 ppm or less, 4g) was charged therein, further ZrO₂ balls (φ=5 mm, 53 g) were chargedtherein, and the vessel was completely hermetically sealed. The vesselwas installed on a satellite ball mill machine (trade name: P7,manufactured by Fritsch Gmbh), and the mechanical milling was conductedat 500 rpm of the base for 40 hours. After that, the mixture was driedat 100° C. to remove heptane to obtain sulfide glass.

Then, 0.5 g of the resulted sulfide glass was charged in a glass tube,and the glass tube was charged in a hermetically sealed SUS vessel. Thehermetically sealed vessel was heated at 190° C. for 10 hours and glassceramics was obtained. A molar composition of the resulted glassceramics corresponds to x=14 in xLiI·(100−x)(0.75Li₂S·0.25P₂S₅).

Examples 2 to 5

Glass ceramics were obtained in a manner similar to that of Example 1,except that a ratio of LiI in xLi·(100−x)(0.75Li₂S·0.25P₂S₅) was changedto x=15, 20, 24, and 25, respectively, and the heat treatmenttemperature was changed to the temperatures described in Table 1respectively.

Comparative Examples 1 to 4

Sulfide glasses were obtained in a manner similar to that of Example 1,except that a ratio of LiI in xLi·(100−x)(0.75Li₂S·0.25P₂S₅) was changedto x=0, 10, 13, and 30, respectively, and the heat treatment temperaturewas changed to the temperatures described in Table 1 respectively.

Comparative Examples 5 to 9

Sulfide glasses were obtained in a manner similar to that of Example 1,except that a ratio of LiI in xLiI·(100−x)(0.75Li₂S·0.25P₂S₅) waschanged to x=0, 10, 20, 30, and 40, respectively. Thereafter, withoutconducting the heat treatment, the sulfide glasses were prepared asreference samples.

TABLE 1 Ratio of LiI Li₂S P₂S₅ Heat treatment LiX x⁽¹⁾ State⁽²⁾ (g) (g)(g) temperature (° C.) Example 1 14 A 0.390 0.616 0.994 190 Example 2 15A 0.416 0.606 0.978 190 Example 3 20 A 0.542 0.558 0.900 180 Example 424 A 0.639 0.521 0.840 170 Example 5 25 A 0.663 0.512 0.825 180Comparative 0 A 0.000 0.766 1.234 220 Example 1 Comparative 10 A 0.2840.657 1.059 200 Example 2 Comparative 13 A 0.364 0.626 1.010 195 Example3 Comparative 30 A 0.778 0.468 0.754 200 Example 4 Comparative 0 B 0.0000.766 1.234 — Example 5 Comparative 10 B 0.284 0.657 1.059 — Example 6Comparative 20 B 0.542 0.558 0.900 — Example 7 Comparative 30 B 0.7780.468 0.754 — Example 8 Comparative 40 B 0.996 0.385 0.620 — Example 9⁽¹⁾x in xLiI · (100 − x)(0.75Li₂S•0.25P₂S₅) ⁽²⁾A = glass ceramics, B =sulfide glass

[Evaluation 1]

(X-Ray Diffraction Measurement)

X-ray diffraction (XRD) measurements with CuKα line were conducted onthe glass ceramics obtained in Examples 1 to 5 and Comparative Examples2 to 4. In the XRD measurement, RINT Ultima III (trade name,manufactured by Rigaku Corporation) was used. Results thereof are shownin FIG. 3 and FIG. 4. As illustrated in FIG. 3, it was confirmed thateach of the glass ceramics obtained in Examples 1 to 5 has peaks of acrystalline phase having high Li ion conductivity at 2θ=20.2° and 23.6°.On the other hand, as illustrated in FIG. 4, in the glass ceramicsobtained in Comparative Examples 2 to 4, the peaks of the crystallinephase having the high Li ion conductivity were not confirmed, and onlypeaks of a crystalline phase having low Li ion conductivity at 2θ=21.0°and 28.0° were confirmed. Further, from each of the obtained XRD charts,a ratio of a peak intensity at 2θ=20.2° to a peak intensity at 2θ=21.0°(I₂₀₂/I_(21.0)) and a ratio of a peak intensity at 2θ=23.6° to a peakintensity at 2θ=21.0° (I_(23.6)/I_(21.0)) were obtained. Results thereofare shown in Table 2. In Example 1, peaks at 2θ=21.0° and 28.0° were notconfirmed, and accordingly, the ratio of peak intensities was notobtained.

TABLE 2 Ratio of LiI x⁽¹⁾ State⁽²⁾ I_(20.2)/I_(21.0) I_(23.6)/I_(21.0)Example 1 14 A — — Example 2 15 A 2.6 1.1 Example 3 20 A 1.1 0.7 Example4 24 A 1 0.4 Example 5 25 A 0.3 0.2 Comparative 0 A 0 0 Example 1Comparative 10 A 0 0 Example 2 Comparative 13 A 0 0 Example 3Comparative 30 A 0 0 Example 4 ⁽¹⁾x in xLiI · (100 − x)(0.75Li₂S ·0.25P₂S₅) ⁽²⁾A = glass ceramics

(Measurement of Li Ion Conductivity)

The Li ion conductivity (at room temperature) was measured on each ofthe samples obtained in Examples 1 to 5 and Comparative Examples 1 to 9by AC impedance method. The Li ion conductivity was measured asdescribed below. Firstly, a sample powder was cold-pressed underpressure of 4 ton/cm² and a pellet having a diameter of 11.29 mm and athickness of about 500 μm was prepared. Next, the pellet was installedin a vessel of inert gas atmosphere, which is filled with Ar gas, toperform measurement. In the measurement, SOLARTRON (trade name: SI1260,manufactured by Toyo Corporation) was used. A measurement temperaturewas controlled to 25° C. by use of a thermostat. Results are shown inTable 3 and FIG. 5.

TABLE 3 Li ion conductivity Ratio of LiX x⁽¹⁾ State⁽²⁾ (S/cm) Example 114 A 2.9 × 10⁻³ Example 2 15 A 3.4 × 10⁻³ Example 3 20 A 3.0 × 10⁻³Example 4 24 A 2.9 × 10⁻³ Example 5 25 A 1.2 × 10⁻³ Comparative 0 A 1.0× 10⁻³ Example 1 Comparative 10 A 1.3 × 10⁻³ Example 2 Comparative 13 A9.6 × 10⁻³ Example 3 Comparative 30 A 3.7 × 10⁻³ Example 4 Comparative 0B 5.0 × 10⁻³ Example 5 Comparative 10 B 6.9 × 10⁻³ Example 6 Comparative20 B 9.7 × 10⁻³ Example 7 Comparative 30 B 1.3 × 10⁻³ Example 8Comparative 40 B 1.0 × 10⁻³ Example 9 ⁽¹⁾x in xLiI · (100 − x)(0.75Li₂S· 0.25P₂S₅) ⁽²⁾A = glass ceramics, B = sulfide glass

As illustrated in Table 3 and FIG. 5, all of the glass ceramics obtainedin Examples 1 to 5 had high Li ion conductivity. This is consideredbecause the glass ceramics obtained in Examples 1 to 5 have acrystalline phase having high Li ion conductivity, which has peaks at2θ=20.2° and 23.6°. Further, the content of LiI x is the same betweenComparative Example 1 and Comparative Example 5, between ComparativeExample 2 and Comparative Example 6, and between Comparative Example 4and Comparative Example 8, respectively. As described above, whensulfide glass doped with LiI is heat-treated, usually, the Li ionconductivity is deteriorated. On the other hand, in the glass ceramicsobtained in Examples 1 to 5, a peculiar behavior that, when the sulfideglass is heat-treated, the Li ion conductivity is improved wasexhibited, and further, the Li ion conductivity was extremely high asthe glass ceramics.

Examples 6 to 8

Glass ceramics were obtained in a manner similar to that of Example 1,except that the ratio of LiI in xLi·(100−x)(0.75Li₂S·0.25P₂S₅) waschanged to x=15, and the heat treatment temperature was changed to 170°C., 180° C. and 190° C., respectively.

Comparative Example 10

Sulfide glass was obtained in a manner similar to that of Example 1,except that the ratio of LiI in xLi·(100−x)(0.75Li₂S·0.25P₂S₅) waschanged to x=15. Thereafter, without conducting the heat treatment,sulfide glass for reference sample was obtained.

Comparative Example 11

Glass ceramics was obtained in a manner similar to that of Example 1,except that the ratio of LiI in xLi·(100−x)(0.75Li₂S·0.25P₂S₅) waschanged to x=15, and the heat treatment temperature was changed to 200°C.

[Evaluation 2]

(X-Ray Diffraction Measurement)

An X-ray diffraction (XRD) measurement with CuKα line was conducted oneach of the glass ceramics obtained in Examples 6 to 8 and ComparativeExample 11. A measurement method was the same as that described in theEvaluation 1. Results are shown in FIG. 6. As illustrated in FIG. 6, itwas confirmed that each of the glass ceramics obtained in Examples 6 to8 has peaks of a crystalline phase having high Li ion conductivity at2θ=20.2° and 23.6°. On the other hand, in the glass ceramics obtained inComparative Example 11, while peaks of the crystalline phase having highLi ion conductivity were not confirmed, only peaks of a crystallinephase having low Li ion conductivity at 2θ=21.0° and 28.0° wereconfirmed.

(Measurement of Li Ion Conductivity)

The Li ion conductivity (room temperature) was measured on each of thesamples obtained in Examples 6 to 8 and Comparative Examples 10 and 11by AC impedance method. The measurement method was the same as thatdescribed in the Evaluation 1. Results thereof are shown in FIG. 7. Asillustrated in FIG. 7, all of the glass ceramics obtained in Examples 6to 8 exhibited the Li ion conductivity higher than that of ComparativeExample 10 in which the heat treatment was not conducted. On the otherhand, in the sample obtained in Comparative Example 11, it is consideredthat the heat treatment temperature was too high to obtain thecrystalline phase having high Li ion conductivity.

1. A sulfide solid electrolyte material comprising: a glass ceramicscontaining Li, A, X and S, wherein A is at least one element of P, Si,Ge, Al, and B, X is a halogen, and the sulfide solid electrolytematerial has peaks at 2θ=20.2° and 23.6° in X-ray diffractionmeasurement with CuKα line. 2-14. (canceled)
 15. The sulfide solidelectrolyte material according to claim 1, wherein a ratio of a peakintensity 2θ=20.2° to a peak intensity at 2θ=21.0° is 1 or more.
 16. Thesulfide solid electrolyte material according to claim 1, wherein thesulfide solid electrolyte material does not substantially containcross-linked sulfur.
 17. The sulfide solid electrolyte materialaccording to claim 1, wherein the glass ceramics includes an ionconductor containing Li, A, and S, and LiX.
 18. The sulfide solidelectrolyte material according to claim 17, wherein a ratio of the LiXis 14% by mole or more and less than 30% by mole.
 19. The sulfide solidelectrolyte material according to claim 18, wherein the ratio of the LiXis more than 14% by mole and less than 30% by mole.
 20. The sulfidesolid electrolyte material according to claim 18, wherein the ratio ofthe LiX is 25% by mole or less.
 21. The sulfide solid electrolytematerial according to claim 17, wherein the ion conductor has an orthocomposition.
 22. The sulfide solid electrolyte material according toclaim 1, wherein the sulfide solid electrolyte material includes 50% bymole or more of a crystalline phase corresponding to the 2θ=20.2° and23.6° relative to a total crystalline phase of the sulfide solidelectrolyte material.
 23. A lithium solid-state battery comprising: apositive electrode active material layer containing a positive electrodeactive material; a negative electrode active material layer containing anegative electrode active material; and a solid electrolyte layerdisposed between the positive electrode active material layer and thenegative electrode active material layer, wherein at least one of thepositive electrode active material layer, the negative electrode activematerial layer, and the solid electrolyte layer includes the sulfidesolid electrolyte material according to claim
 1. 24. A lithiumsolid-state battery comprising: a positive electrode active materiallayer containing a positive electrode active material; a negativeelectrode active material layer containing a negative electrode activematerial; and a solid electrolyte layer disposed between the positiveelectrode active material layer and the negative electrode activematerial layer, wherein at least one of the positive electrode activematerial layer, the negative electrode active material layer, and thesolid electrolyte layer includes the sulfide solid electrolyte materialaccording to claim 21, the LiX is LiI, and the positive electrode activematerial has a potential of 2.8 V or more with respect to Li.
 25. Amethod for producing a sulfide solid electrolyte material includingglass ceramics, the method comprising: amorphizing a raw materialcomposition containing Li₂S, a sulfide of A, and LiX to synthesizesulfide glass; and heating the sulfide glass at a heat treatmenttemperature equal to or more than a crystallization temperature of thesulfide glass to synthesize the glass ceramics having peaks at 2θ=20.2°and 23.6° in X-ray diffraction measurement with CuKα line, wherein A isat least one element of P, Si, Ge, Al and B, X is a halogen, and a ratioof the LiX contained in the raw material composition and the heattreatment temperature are controlled to obtain the glass ceramics. 26.The method according to claim 25, wherein a ratio of a peak intensity2θ=20.2° to a peak intensity at 2θ=21.0° is 1 or more.
 27. The methodaccording to claim 25, wherein the sulfide solid electrolyte materialdoes not substantially contain cross-linked sulfur.
 28. The methodaccording to claim 25, wherein the ratio of the LiX contained in the rawmaterial composition is in a first range of 14% by mole or more and lessthan 30% by mole or in a second range in a vicinity of the first rangeand allows to synthesize the glass ceramics, and an upper limit of theheat treatment temperature is a temperature that allows to synthesizethe glass ceramics in a vicinity of 200° C.
 29. The method according toclaim 25, wherein the ratio of the LiX contained in the raw materialcomposition is 14% by mole or more and less than 30% by mole, and theheat treatment temperature is less than 200° C.
 30. The method accordingto claim 25, wherein the heat treatment temperature is 170° C. or more.31. The method according to claim 25, wherein the heat treatmenttemperature is 190° C. or less.